-Apollo 17 Astronaut Jack Schmitt, after tripping and falling on the moon like someone who is not a highly trained and talented astronaut

The most beautiful words ever written about space travel were crafted with the fervent intent that they would never need to be read.

The United States has never lost an astronaut in space, but the threat has been there in every mission, even one as obsessively planned and triple-checked as Apollo 11, which sent the first men to the moon. The sheer number of things that can go wrong on a manned space mission is in the millions (it’s nearly a miracle that any of the Apollo missions got off the ground, and the program actually started with three fatalities when Apollo 1 burst into flames on the launchpad), but certain failures would have exposed the Apollo astronauts to unique and horrible fates.

So much of space travel relies on a set of cold equations that allow for very little leeway if something goes wrong. Spacecraft are often portrayed in movies as analogous to ships or airplanes, but they’re governed by a unique set of rules. Throttle back on even the fastest of airplanes, for example, and air resistance will slow it down and eventually stop it. Spacecraft have no such restrictions -- if you’re going a hundred thousand miles an hour in a rocket ship, you’ll be at that speed basically forever, unless you crash into something or your craft’s trajectory is altered by a large enough gravitational force. The only way you can slow down is to fire your rockets in the opposite direction, and modern spacecraft don’t have an awful lot in the way of extra fuel to pull this off if something goes wrong. There’s a tense scene in Apollo 13 where astronauts Jim Lovell and Jack Swigert are arguing about their speed and angle of attack upon re-entry -- if they had calculated incorrectly, they would skip off the Earth’s atmosphere like a stone on a lake, only their next destination would have been deep space. They wouldn’t have enough fuel to make another go at it. Apollo 13 would have become a moving tomb, bringing its three imprisoned corpses farther and farther away from their home planet with each passing year.

NASA and the U.S. government in general were well aware of all these potential tragedies, particularly in the case of Apollo 11. No one had attempted to land a manned spacecraft on the moon before; consequently, no one had attempted to lift off from the moon either. Flying, as the airman’s saying goes, is easy; it’s takeoff and landing that are difficult. Had the liftoff rockets on their lunar module failed to fire, Neil Armstrong and Buzz Aldrin would have been stranded on the moon, with no hope of a rescue mission. Michael Collins, in the command module overhead, would have been forced to return home by himself.

What do you say in a situation like that, if you’re Richard Nixon? The idea of casualties is particularly repellent to Americans, and the idea of leaving men behind to die is practically unthinkable. Nixon’s speechwriter, the future columnist William Safire, penned a short statement called “In Event of Moon Disaster”, which Nixon would read in an address to the nation had the worst come to pass. The passage is worth reading in its entirety, but the ending stands out in particular, for its mix of devastating sadness and pioneering defiance:

“In ancient days, men looked at stars and saw their heroes in the constellations. In modern times, we do much the same, but our heroes are epic men of flesh and blood.

Others will follow, and surely find their way home. Man's search will not be denied. But these men were the first, and they will remain the foremost in our hearts.

For every human being who looks up at the moon in the nights to come will know that there is some corner of another world that is forever mankind.”

Fortunately, the rest of the mission went off without a hitch, as did every subsequent Apollo mission save the ill-fated Apollo 13. The danger inherent in the missions never disappeared, but with every time we returned to the moon, the astronauts seemed to have more and more fun with the whole concept.

Take the very next mission after Armstrong and Aldrin walked on the moon. Armstrong’s first words upon descending from the lunar module (“That’s one small step for [a] man, one giant leap for mankind”) were a solemn statement of accomplishment, a verbal flag planted as much on the concept of the moon as the moon itself. Apollo 12 commander Pete Conrad’s first words (“Whoopie! Man, that may have been a small one for Neil, but that's a long one for me!”) were not. He’d let a well-kept secret out: when it’s not ball-crushingly terrifying -- when it’s not trying to asphyxiate you or boil your blood or fry you to death with gamma rays -- space is actually a hell of a lot of fun.

Look, reduced to its simplest parts, modern space travel is this: you strap yourself into a sweet space-suit and climb to the top of a three hundred thousand pound, four hundred foot tall rocket. You push one of a series of cool-looking buttons, and the bottom of the rocket lights the entire world (approximate) on fire, propelling you and your astronaut buddies off the earth with about seven and a half million pounds of force. A minute or so later, you’re weightless, floating in the aether, and then another rocket sends you to the freaking moon, where you get to hop about like an idiot and tool around in a moon buggy like Bo and Luke Duke if Hazzard County was actually in the Sea of Tranquility. One final series of rockets sends you back to earth, and your module burns its way into the atmosphere, where you float into the Pacific Ocean from the end of a big parachute.

To top that off, you then get picked up by guys in scuba-suits, who take you to an aircraft carrier and probably give you hot cocoa.

What I just described would cause a five-year-old to go into paroxysms of glee. Heck, these days, they even give you space ice cream to eat while you’re up there. The few men who actually ended up going to the moon were treated to a mega-continent’s worth of bouncy castle and playground. They had a mission to complete and lists to check off, but that didn’t stop them from occasionally remembering just how absurdly cool it was that they were on the moon. You see their absurdities evolve, little by little -- Conrad’s irreverence was only the beginning. Alan Shepard* snuck a makeshift golf club onto the lunar module during Apollo 14, hitting two shots and sounding ridiculously pleased at the distance he got out of the second one.

*Shepard was something of a celebrity even among other astronauts, which is why NASA probably didn’t even bring up the fact that the club head he snuck on board probably cost a few extra thousand dollars in fuel. It’s tough to get something into orbit -- you need a minimum of four thousand or so dollars of fuel per pound of stuff you want to launch. You’re also subject to some irritating logistical problems -- that fuel has weight too, so it’s launching itself in addition to everything else.

Apollo 15’s David Scott did a live scientific demonstration of the theory of gravity using a hammer and feather, but Jack Schmitt decided to just huck his hammer as far as he could near the end of Apollo 17. Mission Control gave him the go-ahead with kind of an “ah, what the heck” air, although they did offhandedly warn him not to accidentally hit the lunar module with said hammer (even a speechwriter as talented as Safire might be hard-pressed to include that particular detail in an updated space eulogy). Schmitt and fellow astronaut Gene Cernan seemed to have the most fun during their excursion -- singing, falling down, bunny hopping, and generally screwing around.

It’s a pity that we stopped going back to the moon, because the astronauts might have come up with some truly inspired stuff. Familiarity supposedly breeds contempt, but with the astronauts of the Apollo program, it seemed like all it did was make them love the moon more and more each time they went up.

Joe DeMartino is a Connecticut-based writer who grew up wanting to be Ted Williams, but you would not BELIEVE how hard it is to hit a baseball, so he gave that up because he writes words OK. He talks about exploding suns, video games, karaoke, and other cool shit at his blog. He can be emailed at jddemartino@gmail.com and tweeted at @thetoycannon. He writes about sports elsewhere. The sports sells better.